James Cameron is a perfectionist. For his blockbuster movie, “Titanic,” the director spent hours at the bottom of the sea taking notes on the architecture of the ship because he wanted everything to be as accurate as possible. Cameron did an amazing job at recreating the massive ship, but there was one detail that he missed. Luckily, Neil deGrasse Tyson caught it before “Titanic 3D” hit theaters.

Actually, Neil deGrasse Tyson caught the mistake nearly a decade ago when he first watched the movie. Tyson says that Cameron got the night sky wrong during the scene where Kate Winslet is floating on a piece of wood next to the sinking Titanic.

Tyson said:

“There is only one sky that Winslet could have been looking at. And in the movie, it’s the wrong sky. And even worse than that. The left side of the sky is a mirror reflection of the right side.”

Tyson said that he sent Cameron he letter about the error but didn’t get a response. Over the years he ran into Cameron a few times and continually bugged the director about the error until Cameron finally agreed to change the scene.

Cameron said:

“Neil deGrasse Tyson sent me quite a snarky e-mail saying that, at that time of year, in that position in the Atlantic in 1912, when Rose (Kate Winslet) is lying on the piece of driftwood and staring up at the stars, that is not the star field she would have seen… And with my reputation as a perfectionist, I should have known that and I should have put the right star field in. So I said ‘All right, send me the right stars for that exact time and I’ll put it in the movie.’ ”

Here’s a video of Neil deGrasse Tyson explaining how he changed a scene in “Titanic.”